Pressure balanced ultra-short disposable setting tool

ABSTRACT

A setting tool for setting an auxiliary tool in a well, the setting tool including an inner mandrel having an upper section and a lower section, the upper section having an internal chamber suitable for housing a power charge; an outer cylindrical piston enclosing the upper section of the inner mandrel; a slidable ring formed concentrically, and between the inner mandrel and the outer cylindrical piston; and an actuation chamber located between the outer cylindrical piston, the ring, and the inner mandrel. The slidable ring is fixedly attached with a breaking pin to the upper section of the inner mandrel.

BACKGROUND Technical Field

Embodiments of the subject matter disclosed herein generally relate todownhole tools for well operations, and more specifically, to adisposable setting tool used in a well for actuating various auxiliarytools.

Discussion of the Background

During well exploration, various tools are lowered into the well andplaced at desired positions for plugging, perforating, or drilling thewell. These tools are placed inside the well with the help of a conduit,as a wireline, electric line, continuous coiled tubing, threaded workstring, etc. However, some of these tools need to be activated or set inplace. The force needed to activate such a tool is large, for example,in excess of 15,000 lbs. Such a large force cannot be supplied by theconduit noted above.

A setting tool is commonly used in the industry to activate the toolsnoted above. Such a setting tool is typically activated by an explosivecharge that causes a first piston to be driven within the setting tool.The movement of the first piston is transmitted to a second piston, byuse of an oil located between the two pistons. The movement of thesecond piston activates the various tools. A traditional setting tool100 is shown in FIG. 1 and includes a firing head 102 that is connectedto a pressure chamber 104. The firing head 102 ignites a primary igniter103 that in turn ignites a power charge 106. Note that a secondaryigniter may be located between the primary igniter and the power chargeto bolster the igniting effect of the primary igniter.

A mandrel 110 is connected to a housing of the pressure chamber 104 andthis cylinder fluidly communicates with the pressure chamber. Thus, whenthe power charge 106 is ignited, the large pressure generated inside thepressure chamber 104 is guided into the mandrel 110. A floating piston112, which is located inside the mandrel 110, is pushed by the pressureformed in the pressure chamber 104 to the right in the figure. Oil 114stored in a first chamber 115 of the mandrel 110, is pushed through aconnector 116, formed in a block 118, which is located inside themandrel 110, to a second chamber 120. Another piston 122 is located inthe second chamber 120 and under the pressure exerted by the oil 114,the piston 122 and a piston rod 124 exert a large force on a crosslink126. Crosslink 126 can move relative to the mandrel 110 and has asetting mandrel 128 for setting a desired tool (which was discussedabove). Note that mandrel 110 has the end 130 sealed with a cylinderhead 132 that allows the piston rod 124 to move back and forth withoutbeing affected by the wellbore/formation pressure.

After the setting tool has been set, it needs to be raised to thesurface and be reset for another use. Because the burning of the powercharge 106 has created a large pressure inside the pressure chamber 104,this pressure needs to be relieved, the pressure chamber needs to becleaned from the residual explosive and ashes, and the pistons and theoil (hydraulic fluids) need to be returned to their initial positions.

Relieving the high pressure formed in the pressure chamber 104 is notonly dangerous to the health of the workers performing this task,because of the toxic gases left behind by the burning of the powercharge, but is also a safety issue because the pressure in the pressurechamber is high enough to injure the workers if its release is notcarefully controlled. In this regard, note that the traditional settingtool 100 has a release valve 140 that is used for releasing the pressurefrom inside the pressure chamber. However, when the release valve 140 isremoved from cylinder 100, due to the high pressure inside the cylinder,the release valve may behave like a projectile and injure the personremoving it. For this reason, a dedicated removing procedure has beenput in place and also a safety sleeve is used to cover the releasevalve, when at the surface, for relieving the pressure from the settingtool. In addition, the oil contained inside the tool may pose acontamination danger to the environment in case that an internal sealfails.

Thus, another approach is to use a setting tool that self-vents whiledownhole, and/or contains no oil, to avoid the need for redressing atthe surface. However, current disposable setting tools suffer from anumber of drawbacks including high overall tool length, an inability tovent the tool in the event of partial or incomplete activation, and ahigh shock load upon activation. Thus, there is a need for a disposablesetting tool that overcomes these problems.

SUMMARY

According to an embodiment, there is a setting tool for setting anauxiliary tool in a well. The setting tool includes an adaptor sub foraffixing an ignitor, an inner mandrel having an upper section and alower section, the upper section having an internal chamber configuredto house a power charge, and the lower section configured to connect toan adjusted sub for affixing the auxiliary tool, an outer cylindricalpiston slidably located over the inner mandrel, a slidable ring slidablylocated around the upper section of the inner mandrel and fixedlyattached to the outer cylindrical piston, an actuation chamber locatedbetween the inner mandrel and the outer cylindrical piston, and apassage through a wall of the upper section of the inner mandrel,wherein the passage fluidly communicates the internal chamber and theactuation chamber. An activation of the power charge by the ignitorcauses gas to pressurize the actuation chamber and the outer cylindricalpiston to stroke downward to set the auxiliary tool in the well, afterbreaking a breaking pin that holds the slidable ring fixedly attached tothe inner mandrel.

According to another embodiment, there is a setting tool for setting anauxiliary tool in a well, and the setting tool includes an inner mandrelhaving an upper section and a lower section, the upper section having aninternal chamber suitable for housing a power charge, an outercylindrical piston enclosing the upper section of the inner mandrel, aslidable ring formed concentrically, and between the inner mandrel andthe outer cylindrical piston, and an actuation chamber located betweenthe outer cylindrical piston, the ring, and the inner mandrel. Theslidable ring is fixedly attached with a breaking pin to the uppersection of the inner mandrel.

According to still another embodiment, there is a method for using asetting tool in a casing, and the method includes lowering the settingtool into the casing; igniting a power charge located inside an innermandrel of the setting tool; directing a pressured gas, generated by theignited power charge, through a passage formed through a wall of theinner mandrel, to a shoulder of an outer cylindrical piston; actuatingthe outer cylindrical piston with the pressured gas so that the outercylindrical piston moves along the inner mandrel; and setting anauxiliary tool attached to the setting tool when the outer cylindricalpiston is fully stroked. The lower section of the inner mandrel has afirst region having a first thickness T1 and a second region having asmaller second thickness T2, the first region being separated by ashoulder from the second region.

BRIEF DESCRIPTON OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one or more embodiments and,together with the description, explain these embodiments. In thedrawings:

FIG. 1 illustrates a traditional setting tool that needs to be retrievedto the surface for removing pressurized gas from inside;

FIG. 2 illustrates a disposable, ultra-short, setting tool, before beingactivated;

FIG. 3 illustrates a detail of the disposable, ultra-short, settingtool, before being activated;

FIG. 4 illustrates a passage formed between an inner mandrel and anouter cylindrical piston of the disposable, ultra-short, setting tool;

FIG. 5 illustrates the disposable, ultra-short, setting tool after beingactivated;

FIG. 6 illustrates a detail of the disposable, ultra-short, setting toolafter being activated;

FIG. 7 illustrates a venting mechanism of the disposable, ultra-short,setting tool;

FIG. 8 illustrates the disposable, ultra-short, setting tool having twoventing mechanisms, in the run-in state;

FIG. 9 illustrates the disposable, ultra-short, setting tool having twoventing mechanisms, in the fully stroke state;

FIG. 10 illustrates slots formed in the upper section of the innermandrel for the second venting mechanism; and

FIG. 11 is a flowchart of a method for using the disposable,ultra-short, setting tool.

DETAILED DESCRIPTION

The following description of the embodiments refers to the accompanyingdrawings. The same reference numbers in different drawings identify thesame or similar elements. The following detailed description does notlimit the invention. Instead, the scope of the invention is defined bythe appended claims. The following embodiments are discussed, forsimplicity, with regard to a setting tool. However, the embodimentsdiscussed herein are also applicable to any tool in which ahigh-pressure is generated and then that high-pressure needs to betransferred to a piston without the presence of an oil.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with an embodiment is included in at least oneembodiment of the subject matter disclosed. Thus, the appearance of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout the specification is not necessarily referring to the sameembodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

According to an embodiment, a setting tool for setting an auxiliary tool(e.g., a plug) in a well includes an inner mandrel having an uppersection and a lower section, the upper section having an internalchamber suitable for housing a power charge, and the lower sectionconfigured to connect to a sub for affixing an auxiliary tool, acylindrical piston configured to slide along the inner mandrel, anannular activation chamber located between the cylindrical piston andthe inner mandrel, and a gas port formed through a wall of the innermandrel, to provide a fluid communication path between the inner mandrelinternal chamber and the annular actuation chamber defined by thecylindrical piston. Activation of the power charge by the ignitor causespressurized gas to enter the actuation chamber and the cylindricalpiston to stroke downward to set the auxiliary tool in the well.

An embodiment of a setting tool 200 is shown in FIG. 2 in a preactivatedstate as the setting tool is run into the casing 202 (note that forsimplicity, FIG. 2 shows only the bottom part of the casing, and not theupper part). The left hand side in the figure is facing the upper partof the well (i.e., the head) and the right hand side is facing the lowerpart of the well (i.e., the toe). In this embodiment, the setting tool200 contains no hydraulic fluid (e.g., no oil) and thus, it may bereadily disposed of after use, without a redressing operation, which isdangerous to the operator, as discussed in the Background section.Further, because the setting tool includes no oil, the disposaloperation does not raise environmental issues. The term “disposablesetting tool” is interpreted in this document to mean a setting toolthat does not store oil (a hydraulic fluid) for acting on a piston.

In the configuration shown in FIG. 2, the setting tool 200 may beprovided with an adaptor sub 210 configured to accept an S1® Ignitor 212manufactured by the present applicant GEODynamics and described in U.S.Pat. No. 10,003,236, which is incorporated herein. Other types ofignitors 212 and firing devices may be readily accepted in the adaptorsub 210 as shown. Alternatively, the setting tool 200 is provided aloneand is configured to accept common industry firing heads, devices, orsubs. In this embodiment, the S1 ignitor 212 is installed into theprovided adaptor sub 210 located at the uphole end of the setting tool.Note that “upper” or “uphole” end are terms used herein to mean to theleft as shown in a figure and this end corresponds to a higher level ina vertical well, or towards the heel when discussing a lateral portionof a well. Conversely, “lower” or “downhole” end refer to a lowerposition, to the right of a figure, or further down a well towards theend or toe of the well. The adaptor sub 210 is configured to connectwith appropriate threads to a casing element.

The adaptor sub 210 includes a head 214 that holds the ignitor 212 andis configured to be attached by threads 214′ to corresponding threads223 of an inner mandrel 220. A power charge 216 is located, in thisembodiment, within the inner mandrel 220 of the setting tool 200. In oneembodiment, the entire power charge 216 may be located within the innermandrel 220. The inner mandrel 220 has two sections, an upper section222 and a lower section 224. The upper section 222 forms a power chargechamber 230, which is filled with the power charger 216, and the powercharge chamber 230 terminates at a first blind end 232. In thisembodiment, the power charge 216 is not located within the head 214 ofthe adaptor sub 210, as also shown in FIG. 2. Opposite the first blindend 232 is a wall 234 separating a second blind end 236, which definesan auxiliary chamber 238. The second blind end 236 marks the beginningof the lower section 224 of the inner mandrel 220. The lower section 224is configured with threads 225 to accept an adjuster sub 240 forconnection to a downhole auxiliary tool such as a frac or bridge plug orother device to be set within the casing (not shown). The upper section222 is configured with threads 223 for connecting to the adaptor sub210.

An outer cylindrical piston 250 is configured to enclose the uppersection 222 of the inner mandrel 220 when the setting tool is notactuated. In one embodiment, the outer cylindrical piston 250 is placedcoaxial with the power charge 216. The outer cylindrical piston 250 isformed a single piece, having an interior shoulder 256, formed at alower end 250A, and the shoulder is configured to extend radially,toward the inner mandrel 222. In one embodiment, the interior shoulder256 is configured to touch the inner mandrel 222 and slide along itslongitudinal axis X. The outer cylindrical piston 250 forms a dampeningchamber 258 with the upper section 222 of the inner mandrel 220. Thedampening chamber 258 is shaped as an annulus chamber. Note that thedampening chamber 258 is filled with air at atmospheric pressure, andwhen the outer cylindrical piston 250 is actuated, the volume of thedampening chamber 258 decreases. With the air inside the dampeningchamber 258 having no way to escape, it compresses, thus increasing itspressure, which acts as a dampening on the outer cylindrical piston 250.

The upper end 250B of the outer cylindrical piston 250, which is shownin more detail in FIG. 3, has threads 252 that are configured to engagecorresponding threads 262 of a slidable ring 260, which is configured tofully encircle a portion of the upper section 222 of the inner mandrel220. The slidable ring 260 is sandwiched between the upper section 222of the inner mandrel 220 and the upper end 250B of the outer cylindricalpiston 250 as shown in FIGS. 2 and 3. Because of the mating threads 252and 262, the outer cylindrical piston 250 is fixedly attached to theslidable ring 260, and they move in tandem when the setting tool isactivated.

Those skilled in the field will know that when the setting tool islowered into the casing, the outer cylindrical piston 250 may touch thecasing 202, which may result in accidentally moving the piston relativeto the inner mandrel. To prevent the outer cylindrical piston 250 frommoving while the setting tool is lowered into the casing, the slidablering 260 is fixed with a breakable pin 264 to the upper section 222 ofthe inner mandrel 220. In this regard, FIG. 3 shows that a through hole254 is formed at the upper end 250B of the outer cylindrical piston 250,and a receiving hole 226 is formed into the upper section 222. Thethrough hole 254 is aligned with the receiving hole 226 so that thebreakable pin 264 can be inserted from outside the outer cylindricalpiston 250, into the upper end 250B and into the receiving hole 226, sothat the slidable ring 264 is fixed relative to the upper section 222. Astrength of the breakable pin 264 is selected so that a pressured gasformed as a consequence of the ignition of the power charge 216 iscapable to break the pin 264 and actuate the outer cylindrical piston250, as discussed later.

FIG. 3 also shows first and second seals 265 and 267 placed atinterfaces between the slidable ring 264 and the upper end 250B of theouter cylindrical piston 250, and the slidable ring 264 and the uppersection 222 of the inner mandrel 220, to prevent the pressured gas toescape from the setting tool.

The lower end 250A of the outer cylindrical piston 250 and thecorresponding part of the upper section 222 that faces the outercylindrical piston 250, are shown in more detail in FIG. 4. One or morepassages 402 are formed between the power charge chamber 230 and anactuation chamber 410 formed between the outer cylindrical piston 250and the upper section 222 of the inner mandrel 220. The actuationchamber 410 is closed along the X axis by the shoulder 256 of the outercylindrical piston 250, at the lower end, and by a shoulder 228 formedinto the upper section 222 of the inner mandrel 220, at the upper end.The shoulder 228 of the upper section 222 extends radially, toward theouter cylindrical piston 250, and touches the outer cylindrical piston250. One or more seals 229 are placed between the shoulder 228 and theouter cylindrical piston 250 to prevent a pressured gas from theactuation chamber 410 to escape. Similarly, the shoulder 256 may haveone or more seals 257 facing the upper section 222 to prevent thepressured gas from the actuation chamber 410 to escape.

In its run-in state shown in FIG. 2, the inner mandrel's upper portion222 and the outer cylindrical piston 250 are nested with each other,thus reducing the overall setting tool length L. The term “nest” hereinrefers to the concentric, coaxial arrangement of the outer cylindricalpiston 250 and the upper section of the setting tool in theirpre-activated state. The more concentrically arranged these sectionsinitially results in a shorter setting tool, thus reducing the overalltool string length, which aids in the ability to run the string (havingthe setting tool) into the casing and maneuver the string through bendsand other deviations in the wellbore trajectory. For example, in thisembodiment, the length L of the setting tool is about 20″ and a length Ifrom the top part of the outer cylindrical piston 250 to the top part ofthe adaptor sub 210 is about 6″.

In one or more embodiments, the power charge 216 may be comprised of acompact power charge that when used with the disclosed tool furthernests the mandrel and piston, which results in a setting tool ofsignificantly reduced length. In this embodiment, the length L asmeasured from the upper most end of the inner mandrel 220 to thelowermost end that accepts the adjuster sub 240 measures approximately20 inches. Other reductions in length are readily contemplated by thoseskilled in the art having the benefit of the present disclosure and mayinclude tools of 20 inches or less. Depending upon the setting forcerequired for the given tool to be set, a shorter stroke may be requiredand or less force and thus the power charge requirements may be reduced,thus shortening the tool's length depending upon specific applications.

FIG. 5 shows the setting tool 200 in its fully stroked state followingthe activation of the power charge. Ignitor 212 ignites the power charge216, which results in a pressurized gas being formed within the powercharge chamber 230. The pressurized gas exits the power charge chamber230 along the passage 402 and enters into the actuation chamber 410,which is located outside the inner mandrel 220 and within the outercylindrical piston 250, as illustrated in FIG. 5. The pressured gasdirectly strikes the shoulder 256 at the lower end 250A of the outercylindrical piston 250 when entering the actuation chamber 410, whichresults in the downward movement of the outer cylindrical piston 250.Thus, there is no need for any oil to activate the outer cylindricalpiston 250. The path of the pressured gas, from the power charge chamber230 to the actuation chamber 310 is illustrated by arrows in FIG. 5.

To be able to actuate the outer cylindrical piston 250, the pressuredgas needs to generate a force large enough to break the breaking pin264. FIG. 5 shows that the breaking pin 264 has been broken, with onepiece 264A still seen inside the receiving hole 226 and with anotherpiece 264B still inside the hole 254 of the upper end 250B of the outercylindrical piston 250. FIG. 5 further shows that the slidable ring 260moves in tandem with the outer cylindrical piston 250, in a downwarddirection, until the slidable ring 260 is stopped by the shoulder 228 ofthe upper section 222 of the inner mandrel 220. The air trapped insidethe dampening chamber 258 is compressed during the actuation of thesetting tool, which may act as a dampening mechanism so that the outercylindrical piston 250 does not slam violently the shoulder 228 of theupper section 222 of the inner mandrel 220.

In one embodiment, a damping element 270 may be placed between (1) theslidable ring 260 and the shoulder 228, and/or (2) the shoulder 256 andthe upper end of the adjuster sub 240. For simplicity, FIG. 5 shows thedamping element 270 placed at the later position. However, the dampingelement 270 is optional.

As mentioned above, the setting tool 200 has the ability to self-ventthe pressurized gases while still downhole, following activation. Thisis achieved by the venting mechanism 500, which is partially implementedat the shoulder 256 as now discussed with regard to FIG. 6. In thisimplementation, as illustrated in FIG. 6, the venting mechanism 500includes a step down in the thickness of the lower section 224 of theinner mandrel 220, from a first thickness T1 to a smaller thickness T2,so that a passage 510 (or annulus) is formed between the shoulder 256 ofthe outer cylindrical piston 250 and the outer surface of the lowersection 224 of the inner mandrel 220. A shoulder 502 defines thereduction in thickness of the lower section 224 of the inner mandrel220. When the face of the shoulder 256, which fits tightly to the uppersection 224 of the inner mandrel 220 prior to passing the shoulder 502,moves downward past the shoulder 502, the passage 510 is formed. At thistime, the actuation chamber 410 automatically becomes fluidly connected,through the passage 510, to an unsealed chamber 520, which is not sealedfrom an exterior of the setting tool. As shown in FIG. 6, the unsealedchamber 520 is defined by the lower end 250A of the outer cylindricalpiston 250, the lower section 224 of the inner mandrel 220, and an endof the adjuster sub 240. An interface 530 between the lower end 250A ofthe outer cylindrical piston 250 and the adjuster sub 240 (shown in thefigure having an exaggerated large gap for illustration) is not sealedso that the pressured gas from the unsealed chamber 520 can escapeoutside the setting tool, as indicated by the arrows in FIG. 6. Theventing mechanism 500 may also be implemented as one or a combination ofa slot, channel or a step down in the diameter of the cylindrical bodyof the barrel piston. Note that the location of the thinner thickness T2of the lower section 224 of the inner mandrel 220 is selected such thatwhen the shoulder 256 of the outer cylindrical piston 250 fully strokespast the shoulder 502 of the lower section 224 of the inner mandrel 220,the gas pressure may thus escape between the two sections and externalto the setting tool. This self-venting is accomplished downhole as partof the activation sequence and thus removes the need to depressurize thesetting tool at the surface.

Returning to FIG. 5, the adaptor sub 212 may include a gas passage 520,which is closed by a cap 522, that allows a secondary manual bleed orvent capability. As discussed above, the setting tool will self-vent(“self-bleed”) gas pressure downhole as part of the activation sequence.However, in certain scenarios, a setting tool may jam or otherwise notfully complete its activation as defined by full extension of its normalstroke. An incomplete stroke thus does not allow a piston or mandrel tofully extend past the point at which the bleed port of valve opens, thusleaving the setting tool in a pressurized state. In that event, thesetting tool must be withdrawn from the well and depressurized forsafety. The present adaptor sub gas passage 520 allow that venting to besafely and readily conducted at the surface in the event of a faulty orincomplete activation.

In one application, the inner mandrel 220 is configured in such a waythat a differential pressure applied on the outer cylindrical piston250, along the longitudinal axis X, by the fluid present inside thecasing is zero or near zero, i.e., the setting tool is pressurebalanced. Note that the differential pressure results because of thehydrostatic pressure that exists in the well and because the traditionalsetting tool has ends having different cross-section areas, whichresults in different forces acting on these ends. Also note that if thisdifferential pressure is not near zero, then the pressured gas in theactuation chamber 410 needs to overcome this differential pressure,which would render the setting tool less efficient. To achieve this nearzero differential pressure, in one embodiment, an external diameter D1of the upper section 222 of the inner mandrel 220 is made to be equal toan external diameter D2 of the lower section 224 of the inner mandrel220, as shown in FIG. 7. Further, the cross-section area 250-1 of theouter cylindrical piston 250 and the cross-section area 260-1 of thering 260, which are perpendicular to the longitudinal axis X, and onwhich the fluid from the casing acts along the longitudinal axis X, aremade to be equal. In this way, the net force exerted along thelongitudinal direction X on the outer cylindrical piston 250, by thefluid present inside the casing, is near zero and thus, the outercylindrical piston 250 is pressured balanced. In one application, abalanced setting tool is achieved if (i) the cross-sectional areas ofthe opposite ends of the outer cylindrical piston 250 are equal or (ii)the external diameters D1 and D2 of the upper and lower sections of thesetting tool are equal. In still another application, both (i) and (ii)need to happen. In yet another application, the near zero differentialpressure may be achieved only if the interface 280 between the ring 260and the outer surface of the upper section 222 of the inner mandrel 220is coplanar with the interface 282 between the shoulder 256 of the outercylindrical piston 250 and the outer surface of the upper section 222 ofthe inner mandrel 220, as also shown in FIG. 7. When the pressurebalanced setting tool is actuated, and the setting tool is connected toa plug, while the setting tool is dangling on a wireline, the outercylindrical piston can do nothing but move down and compress the slipsand packing of the plug. Then, as soon as the plug firmly anchors itselfto the wellbore casing, the outside movement of the outer cylindricalpiston ceases and the inner mandrel can move (pull) back up until theconnection between the setting tool and the plug shears and releases thesetting tool from the plug.

Returning to the damping element 270 discussed above with regard to FIG.5, it may be, for example, an elastomeric grommet, bushing, sleeve,O-ring or a combination of these or other elastomeric elements, that isconfigured to dampen the shock that occurs during the setting toolactivation process. As shown in FIG. 5, for example, the damping element270 is placed concentric to the upper section 222 of the inner mandrel220, so that the ring 260 and the outer cylindrical piston 250 arestopped by the damping element 270 when fully stroked by the pressurizedgas. Alternatively, the damping element 270 may be attached to the lowerend 250B of outer cylindrical piston 250, to strike the adjusted sub240.

If the pressure increase in the damping chamber 258 is considered to betoo high when the outer cylindrical piston 250 is stroke, so that itmight hinder the piston to fully stroke, it is possible to implement asecond venting mechanism 800, as illustrated in FIG. 8. For thisembodiment, the setting tool 200 is modified to have notches 810 formedin the downhole end of the slidable ring 260 and corresponding slots 820formed in the upper section 222 of the inner mandrel 220, close to theshoulder 228. The slots 820 extend along the axis X and a length of theslots is larger than a length of the slidable ring 260 for the reasonsto be discussed next. In addition, the upper end of the upper section222 has an undercut are 830, such that the inner diameter of thisportion of the upper section is larger than the inner diameter of theremaining of the upper section.

When the outer cylindrical piston 250 is fully stroke as illustrated inFIG. 9, the undercut area 830 fits around the shoulder 228 of the uppersection 222 of the inner mandrel 220. Because of the undercut area 830,a passage 840 is now formed between the actuation chamber 410 and theslots 820, so that the air from the dampening chamber 258 and thepressurized gas existing in the actuation chamber 410 can escape alongslots 820, outside the setting tool, as illustrated by arrows 850.Therefore, the second venting mechanism 800, which includes the notches810, slots 820, undercut area 830, and passage 840 allows thepressurized gas from the actuation chamber 410 to also escape outsidethe setting tool, in addition to the first venting mechanism 500. FIG.10 shows in more detail the position of the slots 820 along the uppersection 222 of the inner mandrel, and also the position of the slidingring 260 relative to the slots 820 when the piston 250 is fully stroke.

A method for setting the setting tool is now discussed with regard toFIG. 11. The method starts in step 1100 by lowering the setting tool 200into the casing 202. The setting tool 200 has an outer cylindricalpiston 250 located over an upper section 222 of an inner mandrel 220.After the setting tool 200 arrives at its final position inside thewell, the power charge 216 stored in the power charge chamber 230 isignited in step 1102. Pressured gas formed within the power chargerchamber 230, as a consequence of the ignition step, is directed in step1104, along the passage 402, to the actuation chamber 410, formedbetween the inner mandrel 220 and the outer cylindrical piston 250, andactuates in step 1106 the outer cylindrical piston 250 to fully stroke.Then, in step 1108, the auxiliary tool (e.g., plug) attached to thesetting tool 200 is set inside the casing.

The disclosed embodiments provide methods and an ultra-short settingtool for well operations in which the setting tool is disposable, i.e.,does not use oil for activating an auxiliary tool. It should beunderstood that this description is not intended to limit the invention.On the contrary, the exemplary embodiments are intended to coveralternatives, modifications and equivalents, which are included in thespirit and scope of the invention as defined by the appended claims.Further, in the detailed description of the exemplary embodiments,numerous specific details are set forth in order to provide acomprehensive understanding of the claimed invention. However, oneskilled in the art would understand that various embodiments may bepracticed without such specific details.

Although the features and elements of the present exemplary embodimentsare described in the embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the embodiments or in various combinations with or withoutother features and elements disclosed herein.

This written description uses examples of the subject matter disclosedto enable any person skilled in the art to practice the same, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the subject matter is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims.

What is claimed is:
 1. A setting tool for setting an auxiliary tool in awell, the setting tool comprising: an adaptor sub for affixing anignitor; an inner mandrel having an upper section and a lower section,the upper section having an internal chamber configured to house a powercharge, and the lower section configured to connect to an adjusted subfor affixing the auxiliary tool; an outer cylindrical piston slidablylocated over the inner mandrel; a slidable ring slidably located aroundthe upper section of the inner mandrel and fixedly attached to the outercylindrical piston; an actuation chamber located between the innermandrel and the outer cylindrical piston; and a passage through a wallof the upper section of the inner mandrel, wherein the passage fluidlycommunicates the internal chamber and the actuation chamber, whereinactivation of the power charge by the ignitor causes gas to pressurizethe actuation chamber and the outer cylindrical piston to strokedownward to set the auxiliary tool in the well, after breaking abreaking pin that holds the slidable ring fixedly attached to the innermandrel.
 2. The setting tool of claim 1, wherein the inner mandrel, theslidable ring, and the outer cylindrical piston are concentricallypositioned, in this order, prior to activation.
 3. The setting tool ofclaim 1, wherein the setting tool contains no hydraulic fluid.
 4. Thesetting tool of claim 1, wherein the adaptor sub further comprises amanual back-off for gas bleeding.
 5. The setting tool of claim 1,wherein the setting tool is self-venting through a venting mechanism. 6.The setting tool of claim 1, wherein the lower section of the innermandrel has a first region having a first thickness T1 and a secondregion having a smaller second thickness T2, the first region beingseparated by a shoulder from the second region.
 7. The setting tool ofclaim 6, wherein the outer cylindrical piston (250) has a shoulder thatextends radially toward the inner mandrel.
 8. The setting tool of claim7, wherein the shoulder of the outer cylindrical piston is configured tocontact the first region of the lower section when the outer cylindricalpiston is sliding along the first region, and to not contact the secondregion of the lower section when the outer cylindrical piston is slidingalong the second region.
 9. The setting tool of claim 8, wherein thepressured gas from the actuation chamber is (1) prevented to escape whenthe shoulder of the outer cylindrical piston is in contact with thefirst region of the lower section of the inner mandrel, and (2) allowedto escape from the actuation chamber, through a passage, when theshoulder of the outer cylindrical piston is not in contact with thesecond region of the lower section of the inner mandrel.
 10. The settingtool of claim 1, further comprising a first venting mechanism located atan interface between the outer cylindrical piston and an adjuster sub,which is attached at the lower section of the inner mandrel, wherein thefirst venting mechanism is closed when the outer cylindrical piston isnot actuated, and the first venting mechanism is open when the outercylindrical piston is fully stroked.
 11. The setting tool of claim 10,further comprising a second venting mechanism located at an interfacebetween the outer cylindrical piston, the slidable ring, and the uppersection of the inner mandrel, wherein the second venting mechanism isclosed when the outer cylindrical piston is not actuated, and the secondventing mechanism is open when the outer cylindrical piston is fullystroked.
 12. The setting tool of claim 1, further comprising: adampening element located between the slidable ring and the innermandrel so that when the outer cylindrical piston is fully stroked, theslidable ring squeezes the dampening element against a shoulder of theinner mandrel.
 13. A setting tool for setting an auxiliary tool in awell, the setting tool comprising: an inner mandrel having an uppersection and a lower section, the upper section having an internalchamber suitable for housing a power charge; an outer cylindrical pistonenclosing the upper section of the inner mandrel; a slidable ring formedconcentrically, and between the inner mandrel and the outer cylindricalpiston; and an actuation chamber located between the outer cylindricalpiston, the ring, and the inner mandrel, wherein the setting tool issized to be pressure balanced when placed in the well.
 14. The settingtool of claim 13, wherein the setting tool is pressure balanced when (i)the outer cylindrical piston is sized so that cross-sectional areas ofopposite ends are equal, or (ii) an outer diameter of the upper sectionof the inner mandrel is equal to an outer diameter of the lower sectionof the inner mandrel, or (iii) the outer cylindrical piston is sized sothat cross-sectional areas of opposite ends are equal, and an outerdiameter of the upper section of the inner mandrel is equal to an outerdiameter of the lower section of the inner mandrel.
 15. The setting toolof claim 13, further comprising: a passage formed through a wall of theupper section of the inner mandrel, wherein the passage is fluidlyconnected to the actuation chamber.
 16. The setting tool of claim 13,wherein the lower section of the inner mandrel has a first region havinga first thickness T1 and a second region having a smaller secondthickness T2, the first region being separated by a shoulder from thesecond region.
 17. The setting tool of claim 16, wherein the outercylindrical piston has a shoulder that extends radially toward the innermandrel, and the shoulder of the outer cylindrical piston is configuredto contact the first region of the lower section when the outercylindrical piston is sliding along the first region, and to not contactthe second region of the lower section when the outer cylindrical pistonis sliding along the second region.
 18. The setting tool of claim 17,wherein the pressured gas from the actuation chamber is (1) prevented toescape when the shoulder of the outer cylindrical piston is in contactwith the first region of the lower section of the inner mandrel, and (2)allowed to escape from the actuation chamber, through a passage, whenthe shoulder of the outer cylindrical piston is located over the secondregion of the lower section of the inner mandrel.
 19. The setting toolof claim 13, further comprising: an adaptor sub attached to the tread ofthe inner mandrel; and an adjuster sub attached to a lower end of theinner mandrel.
 20. The setting tool of claim 19, further comprising: anignitor located in the adaptor sub; and the power charge located withinthe internal chamber, wherein activation of the power charge by theignitor causes gas to pressurize the actuation chamber and the outercylindrical piston to stroke downward to set the auxiliary tool in thewell.
 21. The setting tool of claim 13, further comprising: a dampeningelement located between the slidable ring and a shoulder of the innermandrel so that when the outer cylindrical piston is fully stroked, theslidable ring squeezes the dampening element against the shoulder of theinner mandrel.
 22. The setting tool of claim 13, further comprising: afirst venting mechanism located at an interface between the outercylindrical piston and an adjuster sub attached to the lower section ofthe inner mandrel, the first venting mechanism being configured to allowthe pressured gas from the activation chamber to escape from the settingtool, wherein the first venting mechanism is closed when the outercylindrical piston is not actuated, and the first venting mechanism isopen when the outer cylindrical piston is fully stroked.
 23. The settingtool of claim 21, further comprising: a second venting mechanism locatedat an interface between the outer cylindrical piston, the slidable ring,and the upper section of the inner mandrel, wherein the second ventingmechanism is closed when the outer cylindrical piston is not actuated,and the second venting mechanism is open when the outer cylindricalpiston is fully stroked.
 24. A method for using a setting tool in acasing, the method comprising: lowering the setting tool into thecasing; igniting a power charge located inside an inner mandrel of thesetting tool; directing a pressured gas, generated by the ignited powercharge, through a passage formed through a wall of the inner mandrel, toa shoulder of an outer cylindrical piston; actuating the outercylindrical piston with the pressured gas so that the outer cylindricalpiston moves along the inner mandrel; and setting an auxiliary toolattached to the setting tool when the outer cylindrical piston is fullystroked, wherein the lower section of the inner mandrel has a firstregion having a first thickness T1 and a second region having a smallersecond thickness T2, the first region being separated by a shoulder fromthe second region.